The present invention relates to a developer which develops an electrostatic latent image on a photosensitive drum in an electrophotography machine, and more particularly to a device for informing whether fresh toner should be newly supplied into the developer.
Referring to FIG. 1, a conventional developer 1 includes a sleeve 4 for delivering toner 7 to a photosensitive drum 3, a blade 5 for regulating the distribution of the toner 7 deposited on the sleeve 4, an agitator 6 for agitating the toner 7, a hopper 2 for loading the toner, and a toner sensor 8 mounted on an inside wall of the hopper below the agitator 6. The toner sensor 8 consists of a piezoelectric element that is subjected to the pressure of the toner 7 in the hopper so as to generate a voltage informing whether the toner is existent or not in the hopper by consuming. Namely the weight of the toner in the hopper actuates the piezoelectric element to generate the voltage. The voltage from the piezoelectric element is applied to a central processing unit (CPU) so as to turn on an indicating lamp for user for indicating the existence of sufficient amount of the toner in the hopper 2. On the other hands, if there is no toner in the hopper, the piezoelectric element does not generate the voltage so that the indicating lamp is turned off.
Another conventional device for informing whether ferritic toner is existent or not in the hopper includes, as shown in FIG. 2, a photosensor 8 pivotally moved with a pivot pin, and an actuator 10 with a magnet 9 at one side thereof and with a light shield 12 for shielding a light at another side thereof. When the ferritic toner 7 is loaded into the hopper 2, the ferritic toner attracts the magnet 9 so as to cause the light shield 12 to prevent the photosensor from receiving the light. Hence an indicating lamp is turned on for user for indicating the existence of sufficient amount of the ferritic toner in the hopper. Conversely, if there is no ferritic toner 7 the hopper 2, the magnet 9 is separated from the bottom of the hopper 2 so as to cause the light shield 12 to move away from the photosensor. Accordingly, the indicating lamp is turned off.
In these two conventional devices, the former has the drawbacks that the piezoelectric element is very expensive compared to the photosensor. Further, it is very difficult to install the piezoelectric element within the hopper, and the output voltage of the piezoelectric element varies with the loaded amount of the toner, thus resulting in technical complexity. Meanwhile the latter must use only the ferritic toner.